How do I play Sudoku?

Fill every row, column and 3×3 box with the digits 1 through 9 exactly once. Start with the given digits, use notes for candidates, and never repeat a digit in a unit.

Does this Sudoku have one solution?

Yes. The generator removes clues only while a bounded solver still finds exactly one solution. The same solution is used for the completion check and hints.

Can I use pencil marks and undo?

Yes. Notes are independent from answers, and Undo restores either a digit or a note change. Hints are marked as assisted.

Is my Sudoku progress saved?

The current puzzle, entries, notes, timer and assisted state are saved in this browser only. There is no account or server sync.

Sudoku Online

Play an original 9×9 Sudoku puzzle in your browser. Choose Easy, Medium or Hard, enter digits with the keyboard or buttons, keep pencil notes, undo assisted actions, and ask for a hint when you need one. Every generated board has exactly one solution, the timer and progress stay only in this browser, and a revealed answer marks the session assisted so the result remains honest. Difficulty is defined by the implemented generator and clue count, not by an unmeasured claim about human solving time.

SUDOKU · LOCAL PUZZLE

Fill every row, column and box

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Difficulty

Choose a square, then press a number.

Keyboard: focus the board, use arrows to choose a square, then press 1–9. Notes are local pencil marks. Every generated puzzle has exactly one solution; difficulty is based on clue count and the generator's bounded uniqueness check.

Common questions

How do I play Sudoku?: Fill every row, column and 3×3 box with the digits 1 through 9 exactly once. Start with the given digits, use notes for candidates, and never repeat a digit in a unit.
Does this Sudoku have one solution?: Yes. The generator removes clues only while a bounded solver still finds exactly one solution. The same solution is used for the completion check and hints.
Can I use pencil marks and undo?: Yes. Notes are independent from answers, and Undo restores either a digit or a note change. Hints are marked as assisted.
Is my Sudoku progress saved?: The current puzzle, entries, notes, timer and assisted state are saved in this browser only. There is no account or server sync.

Every generated puzzle has exactly one solution and every given agrees with that solution. Conflicts are checked by row, column and 3×3 box; difficulty is a tested generator setting rather than a universal human rating.